During a typical dental implantation procedure, the tissue surrounding the jawbone is cut to expose the implantation site. A hole is drilled into the bone, and a dental implant is positioned into this hole. The tissue is then sutured, and the implant is left in the bone for several months as healing and osseointegration occur. During this healing period, a prosthesis or artificial tooth is custom made to fit in the patient's mouth. During a second surgical procedure, the tissue surrounding the implantation site is again cut. The prosthesis is then connected to the end of the implant.
Typically, a dental abutment is located between the implant and prosthesis. The abutment serves several functions but generally provides a structure for extending the implant above the gum-line. One end of the abutment connects to the implant while a second end of the abutment connects to the prosthesis. Typically, a screw holds the abutment to the implant, and either another screw or cement holds the abutment to the prosthesis.
Abutments may have numerous configurations, but generally they have a straight or angled cylindrical configuration. U.S. Pat. No. 5,069,622 entitled "Spacer" to Rangert et al. illustrates an angled abutment, shown in FIG. 1 (prior art).
FIG. 1 shows a one-piece angled abutment at 10. This abutment includes a conical base portion 12 and a conical upper portion 14. These two portions are not removable from one another and are formed together to make a unitary member.
A first bore 16 extends downwardly through both the base and upper portions, and a second threaded bore 18 extends through the upper portion. The base portion 12 has a conical shape and includes a bottom surface 20 that abuts against the end of an implant (not shown). An interior portion of the bottom of bore 16 has a non-cylindrical shape 22 to provide anti-rotational engagement between the abutment and implant. A screw (not shown) passes into bore 16, abuts against a ledge 24, and holds the abutment to the implant.
The upper portion 14 tapers away from the base portion at a preselected angle, preferably between 25.degree. and 40.degree.. The prosthesis fits around the upper portion and abuts against a ledge 26 at the top of the base portion. A screw (not shown) passes into a threaded bore 18 to hold the prosthesis to the abutment.
One important disadvantage with prior straight and angled abutments is that the base portion cannot be removed from the upper portion. In some instances, however, the base portion needs to be removed or replaced. For example, the tissue surrounding the base of the abutment tends to recede over time. As this tissue recedes, more and more of the abutment is visible in the patient's mouth. The abutment, usually made of the metal titanium, has an unappealing appearance and disrupts the aesthetic quality of the prosthesis.
As another disadvantage, prior abutments have base and upper portions made from the same material. Generally, the abutments are formed as a solid piece of titanium or other suitable material. Numerous advantages could be realized if the base portion were formed from one material while the upper portion were formed from another material.
As another disadvantage, prior abutments are not well suited to have the base portion colored or coated while leaving the upper portion uncolored or uncoated.
The present invention solves the problems discussed above with prior dental abutments and provides further advantages.